EP 0247528 B1 19900221 - POLYCRYSTALLINE SINTERED ARTICLES BASED ON SILICON NITRIDE WITH HIGH RUPTURE STRENGTH AND HARDNESS
Title (en)
POLYCRYSTALLINE SINTERED ARTICLES BASED ON SILICON NITRIDE WITH HIGH RUPTURE STRENGTH AND HARDNESS
Publication
Application
Priority
DE 3617282 A 19860523
Abstract (en)
[origin: US4743571A] Polycrystalline sintered bodies are provided consisting of at least 66% by weight of a crystalline Si3N4 phase, of which at least 90% by weight is in the beta-modification, and of up to 34% by weight of secondary intergranular grain boundary phases of oxide, carbide and/or nitride. At least 25% by weight of the secondary grain boundary phases consists of a quasi-ternary crystalline compound in the E1-E2-E3 triangle of the Ga2O3-La2O3-Al2O3 ternary system called "Gala", the "Gala" compound being prepared from gallium oxide, lanthanum oxide and aluminum oxide prior to producing the sintered bodies. The polycrystalline sintered bodies are produced by sintering with and without application of pressure from silicon nitride powders having a portion of impurities not exceeding 4.0% by weight, sintering additives of oxides and optionally other refractory admixtures of carbides and/or nitrides. Powders of a quasi-ternary crystalline compound (Gala compound) are employed as at least one sintering additive prepared, prior to mixing with the remaining components and to sintering, from gallium oxide, lanthanum oxide and aluminum oxide by heating to temperatures from 1500 DEG C. to 1850 DEG C. When using at least 70% by weight of silicon nitride powder, there can be used up to 30% by weight of a crystalline "Gala" compound alone or mixed with other admixtures of oxides, carbides or nitrides, but altogether at least 1% by weight of a crystalline "Gala" compound must be present. The sintered bodies are especially tough and very hard and can be used for the machining of iron materials at high cutting speeds.
IPC 1-7
IPC 8 full level
C04B 35/58 (2006.01); C04B 35/584 (2006.01); C04B 35/593 (2006.01)
CPC (source: EP US)
C04B 35/584 (2013.01 - EP US); C04B 35/593 (2013.01 - EP US); C04B 35/5935 (2013.01 - EP US)
Designated contracting state (EPC)
AT BE CH DE FR GB IT LI NL SE
DOCDB simple family (publication)
EP 0247528 A1 19871202; EP 0247528 B1 19900221; AT E50446 T1 19900315; DE 3617282 A1 19871126; DE 3761727 D1 19900329; JP S62278167 A 19871203; US 4743571 A 19880510
DOCDB simple family (application)
EP 87107429 A 19870522; AT 87107429 T 19870522; DE 3617282 A 19860523; DE 3761727 T 19870522; JP 10338687 A 19870428; US 1948787 A 19870226